* refactor: simplify `QueryChunk` data access
We have only two types for chunks (now that the RUB is gone):
1. In-memory RecordBatches
2. Parquet files
Loads of logic is duplicated in the different `read_filter`
implementations. Also `read_filter` hides a solid amount of logic from
DataFusion, which will prevent certain (future) optimizations. To enable #5897
and to simplify the interface, let the chunks return the data (batches
or metadata for parquet files) directly and let `iox_query` perform the
actual heavy-lifting.
* docs: improve
Co-authored-by: Andrew Lamb <alamb@influxdata.com>
* docs: improve
Co-authored-by: Andrew Lamb <alamb@influxdata.com>
Co-authored-by: Andrew Lamb <alamb@influxdata.com>
Co-authored-by: kodiakhq[bot] <49736102+kodiakhq[bot]@users.noreply.github.com>